*2.4. SEM Images of CS/PVOH/HNT and CS/PVOH/TO@HNT Films*

A Scanning Electron Microscopy (SEM) instrument was used for the surface/crosssection morphology investigation of the pure CS/PVOH film as well as of the CS/PVOH/HNT and CS/PVOH/TO@HNT nanocomposite films. The results confirmed that both HNT and the TO@HNT hybrid nanostructures were homogeneously dispersed in the polymer matrix. The chemical elements of the pure and the final nanocomposite active packaging films were identified by carrying out an Energy dispersive spectrometer (EDS) analysis on the surface of the materials.

The SEM images in Figure 4a,b show the expected smooth morphology of the neat polymer. The EDS spectra in Figure 4c certify the existence of carbon (C), and oxygen (O). *Gels* **2022**, *8*, x FOR PEER REVIEW 7 of 25

Surface and relative cross-section images of CS/PVOH/HNT and CS/PVOH/TO@HNT with different ratios of HNT and TO@HNT are presented in Figures 5–7. Figures 5e,f–7e,f show EDS chemical analysis of nanocomposite active packaging films with different concentrations of pure HNT and TO@HNT hybrid nanostructure i.e., 5, 10, and 15 wt.%. The presence of typical elements such as Si, Al, O, Fe, and Ca was Surface and relative cross-section images of CS/PVOH/HNT and CS/PVOH /TO@HNT with different ratios of HNT and TO@HNT are presented in Figures 5–7. Figures 5–7e,f show EDS chemical analysis of nanocomposite active packaging films with different concentrations of pure HNT and TO@HNT hybrid nanostructure i.e., 5, 10, and 15 wt.%. The presence of typical elements such as Si, Al, O, Fe, and Ca was confirmed.

confirmed. As illustrated in Figures 5–7, the content of both HNT and TO@HNT increases the aggregation of the obtained CS/PVOH/HNT, and CS/PVOH/TO@HNT nanocomposites decrease further. Nevertheless, SEM images of the final nanocomposite films show that both pure HNT and TO@HNT nanohybrid were homogeneously dispersed and suggest enhanced compatibility with the polymer matrix. Moreover, SEM surface and cross-section images were shown more homogenous dispersion in the case of TO@HNT hybrid nanostructure in nanocomposite films compared to the relevant of pure HNT. This means that the TO@HNT hybrid nanostructure was incorporated significantly better in the polymer matrix compared to the incorporation of the respective pure HNT.

**Figure 5.** (**a**,**c**) SEM images of the surface and (**b**,**d**) cross-section for the nanocomposite films of ALG/G/5HNTNZ (**a**,**b**) and ALG/G/5TO@HNT (**c**,**d**) respectively. (**e**,**f**) Energy dispersive spectrometer (EDS) spectrum and relative elemental analysis of the surface (inset) from the SEM images (**a**,**c**). **Figure 5.** (**a**,**c**) SEM images of the surface and (**b**,**d**) cross-section for the nanocomposite films of ALG/G/5HNTNZ (**a**,**b**) and ALG/G/5TO@HNT (**c**,**d**) respectively. (**e**,**f**) Energy dispersive spectrometer (EDS) spectrum and relative elemental analysis of the surface (inset) from the SEM images (**a**,**c**).

**Figure 6.** (**a**,**c**) SEM images of the surface and (**b**,**d**) cross-section for the nanocomposite films of ALG/G/10HNT (**a**,**b**) and ALG/G/10TO@HNT (**c**,**d**) respectively. (**e**,**f**) Energy dispersive spectrometer (EDS) spectrum and relative elemental analysis of the surface (inset) from the SEM images (**a**,**c**). **Figure 6.** (**a**,**c**) SEM images of the surface and (**b**,**d**) cross-section for the nanocomposite films of ALG/G/10HNT (**a**,**b**) and ALG/G/10TO@HNT (**c**,**d**) respectively. (**e**,**f**) Energy dispersive spectrometer (EDS) spectrum and relative elemental analysis of the surface (inset) from the SEM images (**a**,**c**).

**Figure 7.** (**a**,**c**) SEM images of the surface and (**b**,**d**) cross-section for the nanocomposite films of ALG/G/15HNT (**a**,**b**) and ALG/G/15TO@HNT (**c**,**d**) respectively. (**e**,**f**) Energy dispersive spectrometer (EDS) spectrum and relative elemental analysis of the surface (inset) from the SEM **Figure 7.** (**a**,**c**) SEM images of the surface and (**b**,**d**) cross-section for the nanocomposite films of ALG/G/15HNT (**a**,**b**) and ALG/G/15TO@HNT (**c**,**d**) respectively. (**e**,**f**) Energy dispersive spectrometer (EDS) spectrum and relative elemental analysis of the surface (inset) from the SEM images (**a**,**c**).
